Astronaut calculation help

An 80.0 spacewalking astronaut pushes off a 620 satellite, exerting a 100 force for the 0.590 it takes him to straighten his arms.How far apart are the astronaut and the satellite after 1.20 ?

I know that it involves Newton's 3rd law since the astronaut is applying a force onto the satellite and in turn the satellite pushes back on the astronaut to cause him to move but other that that I'm confused how to solve this problem. If anyone can give me some feedback that would be great!

sorry about forgetting the units.
An 80.0 kg spacewalking astronaut pushes off a 620kg satellite, exerting a 100N force for the 0.590s it takes him to straighten his arms.How far apart are the astronaut and the satellite after 1.20s ?